The Army is working with the Marine Corps as it considers a new service weapon for soldiers, but the commandant says it remains to be seen whether Marines will be equipped with new weapons, too.

During an April 16 hearing, Gen. Jim Amos told the House Armed Services Committee that the Corps is satisfied with the M4 carbine and M16A4 rifle, the 5.56mm weapons that are carried by thousands of Marines in combat. The Corps has no program of record to replace them, and has upgraded them for the last several years, he said.

Still, the Army’s research into a potential next-generation carbine prompted Rep. Joe Wilson, R-S.C., to raise the question on Capitol Hill. The commandant responded that the officials working weapons requirements for the Corps out of Quantico, Va., are “joined at the hip with the Army” on the issue, but that no decision from Marine officials was imminent.

“Right now, we’re aware the Army is doing this. We’re watching it. We’re getting the same reports as they…work their way through this,” Amos said. He added that it is “yet to be seen whether or not we’re going to do this and yet to be seen whether or not we’re going to jump onboard and replace our weapons.”

The Army launched a two-year, $30 million carbine competition in 2011. At the same time, it rolled out plans to begin upgrading its arsenal of M4s into advanced M4A1 carbines, notable for their automatic fire and sturdier barrel and bolt. Army officials intend to announce the competition’s winner this fall, then conduct a cost-benefit analysis to determine whether the service should go with the winner’s weapon or stay with the expanded arsenal of M4A1s.

The Marines have considered a rifle upgrade in the past. The Corps maintains about 200,000 M16s and 80,000 M4s, and in recent years, Marine officials have studied replacing the M16A4’s solid butt stock with an adjustable one to accommodate shorter Marines, and adding a free-floating rail system to the service’s M16s and M4s. Officials also have sought enhancements for eye relief optic mounts. Both sets of ideas were aimed at improving accuracy.

The stopping power of issued rifles is another key concern for Marine brass. In recent years, some senior Marine officials have raised concerns about the stopping power of 5.56mm rounds, while others have said swapping to 7.62mm ammo or another larger caliber creates larger rifle recoil and affects accuracy.

The Corps fields M4s to vehicle operators and other Marines whose jobs render the M16A4 too cumbersome. The trade-off is accuracy and stopping power, of which the M16A4’s longer 20-inch barrel offers more. The M4 has a 14.5-inch barrel, making it difficult for service members to take down targets beyond 200 yards.